This research is designed to substantiate the hypothesis that the level of intrafollicular growth factors and the sensitivity of granulosa cells to their effect are important determinants of the growth of the ovarian follicle. Preliminary evidence suggested that somatomedine=s may be an important determinant of the mitogenic activity of follicular fluid. We will assess the levels of thes mitogens in follicular fluid and culture medium from flooicular cells to assess the possibility that these peptides are secreted locally. To evaluate the sensitivity of granulosa cells to mitogens, we will use cultured cells treated with somatomedins and follicular fluid constituents. Growht curves and thymidine incorporation will be compared. In addition, the influence of growth factors activity on the polyamine biosythetic pathway will be delineated. We hypothesize that this pahtway is an important site for interaction of polypwptide hormones and growth factors in the contrl of follicular growth. Our initial studies on the regulation of the first enzyme in the pathway, ornithine decarboxylase, will now be supplemented by studies of enzyme turnover and half-life as well as assays of polyamine levels and the more distal enzymes in the polyamine pathways. In the latter phases of the work, the techniques described above will be applied to follicular fluid and follicular cells from dissected follicles classified as to degree of atresia. This will allow evaluation of the possibility that growth factor levels and/or cellular sensitivity to their effects are rate-limiting in the growth of atresia of the follicle. In this pahse of the work, the biochemical assays described above will be supplemented with autoradiographic techniques so that granulosa cell replication and ornithine decarbosylase can be localized to growing follicles without disruption of the intrafollicular architecture. These studies will attempt to implicate novel mechanisms in the process by which the follicle destined to ovulate is selected. Physiological interruption of thes mechanisms may result in decreased fertility. since pharmacological inhibitors of the polyamine biosynthetic pathway are available, regulation of fertility at this site may be possible.